Telephone system



Patented Dec. 28, 1926.

UNITE STATES 'FF iil LOUIS A. MORTIMER, 013 NEW YORK, N. Y., ASSXG-NUR,B IEESNE AS$IGNIVIENTS, TO WESTERN ELECTRIC COMPANY, INCORPORATED, AGORBQRATION OF NEXV YORK.

TELEPHONE App c t on filed Fe ruary 9, 19.3 ia Ne 7 This inventionrelates to telephone systems and more particularly to a busy testarrangement for straightforward trunking systems in which a smallernumber of trunk lines are automatically accessible from a larger numberof trunk jacks located at a number of positions in a number ofswitchboards.

ln systems of this general type, automatically operated switches areusuallyemployed whereby when a connection is desired said switches areautomatically operated at the seizure of a jack to hunt for and connectsaid jack with an idle trunk line. The arrangement ofthe jacks at thediiierent boards may be such that a number or" jacks are multipled fromone position to another through a number of boards, and connected to thebrushes of an automatically operated step by step switch and so thatasubsgroup of such jacks and switches are located at one group of boardswhile another sub-group of jacks and switches are located at anothergroup of boards, and so that the terminals of all said switches aremultipled to a single group of trunks.

An object of this invention is to provide a busy test arrangementwhereby if all of the trunks in systems of this type are engaged, a busyindication is established for all of the unused jacks having access tosaid trunks.

Another object of this invention is to provide a busy test indication insysten'is of this type for all of the unused jacks in all subgroupsassociated with a single group of trunks when all of said trunks areengaged regardless of the location of the engaged jacks.

To attain these cordance with one and other objects in feature of thisinvention, there is provided in each trunk hunting switch assigned toserve each set of multiple jacks, a separate terminal bank havingterminals corresponding to the individual trunks; these busy terminalsare multiplied to the corresponding busy terminals of all other switchesin the groups and the brushes of said banks are so arranged that theynormally bridge two adjacent terminals. By means of this bridgingarrangement, if all trunks are engaged, the brushes ot' the specialbanks of the engaged switches will forn'i a complete bridge of themultiple leads corresponding to the total numberor trunks.

Another feature of this invention relates to the provision of meansincluding a common relay which is operated when all trunks are engagedand the terminals of the special banks or the switches employed arebridged together, to apply a busy indication for the jacks in thesubgroups associated with the singlegroup or trunks.

Another feature ofthe invention relates to the arrangement whereby saidbusy indications are given only at the unused jacks of said subgroup andwhereby the jacks associated witht 1e trunks are out off from saidcommon busy indication and given the usual busy test potential on thesleeve leads.

Another feature of the invention resides in the provision of meanswhereby said busy indications may be in the form of a potential or atone, or any other indication on the sleeve leads of the jacks.

Another feature of the invention resides in means whereby the conimonbusy condition is removed as soon as one of the trunks become idle, byoperating the switch that was engaged from the position it occupiedwhile engaged, so as to cause the continuity of the bridge throughterminals of the specialflbanks to be broken, and thus cause the commonrelay to be deenergized and remove the busy condition from the sleevesof the unused jacks.

Re ferring now to the drawings; the circuit shown in Fig. 1 above thedash-dotted li e i dicate one .1 t es ep y s p s c e of one subgrouphaving access to a smaller number of trunks and a series of multiplejacks associated with said switch is shown at th posi fln 0i t ffere o dA and 13,, while the portion below this line shows another switch ofanother sub-group of switches associated with the same number of trunksin thesame manner. The multipling of one of these trunks is shownbetween these two groups of switches, and a similar arrangement ofmultiple jacks are shown at positions of boards C and D. Below thisswitch is shown a relay 50 common to all of these switchesbforestablishing a busy condition in accordance with this invention. Fig. 2illustrates in a schematic manner, the bridging of the terminalscorrespondingto all of the trunks when busy.

This invention has been illustrated in cono io Wit a str gh f war t un ig er tom in which the operators at a large numher of switchboards andpositions have access to a considerably smaller number of outgoingtrunks through step-by-step switches and the busy arrangement has beenshown as applying to this arrangement merely to illustrate one of itsmost useful cmployinents. It should be noted, however, that the systemshown is not inflexible but hat any other arrangements may be made withthe busy arrangement in accordance with this invention applied thereto.To clearly indicate the arrangement of the switches, two sub-groups ofswitchboards A and B and C and D have been shown with a jack at each oftwo positions, at each board, that is, jacks 5 and 6 at board A, jacks 7and 8 at board B, jacks 9 and 10 at board 0 and jacks 11 and 12 at boardD,

he jacks at boards A and B being connected to switch 1 and the jacks atboards C and D being connected to switch 21, while all of the switchesare multipled through trunks such as 100.

An arrangement of this sort may be provided with a number of positionsat boards A, and B and each position may have, for example, twenty jackswith each jackin one position mult-ipled to a corresponding jack in allother positions and the leads from such jacks connected to a switch suchas 1, making a total of twenty switches for these two boards; while inthe two boards C and D, the jacks may be arranged in the same manner,that is, twenty jacks in each PO81 tion multipled to twenty switchesmake a total of 40 switches. These switches may then be associated withtwenty trunks multinled thereto. in this manner any operator at anyposition may make twenty connections through to the twenty trunks ortwenty connections may be extended to the twenty trunks from anycombination of positions. This arrangement may be carried out stillfurther by duplicating these groups of acks at each position and thus,for example, providing jacks at each position through which access maybe had to 100 trunks; Fence, this arrangement is. merely descriptive ofsystems to which the invention may be applied, that is, no matter howmany switches and trunks are arranged at these boards or how many boardsare used, this invention provides an all-trunk busy arrangement wherebybusy potential may be applied to the sleeves of all jacks not used inextend ing a connection and this invention will now be described bytracing a call for one jack for connection with a trunk and laterdescribed llOW the busy arrangement func tions when all trunks areengaged.

. Assuming then that the operator at position 5, for example, hasconnected her cord circuit, not shown, but which may be of any wellknown type, to jack 22, a circuit is es tablished from battery, over thesleeve contacts of the plug of this cord circuit and the jack 22 thrcughthe winding of relay 23, make-before-break contacts of relay 23, commonlead 24, to ground at the armature and back contact of relay 50. Lead24- is shown common to all the switches in the two subgroups of switchesas shown by the taps from this common lead. This circuit causes theoperation of relay 23 which locks up to ground at its left hand armatureand front contact, and disconnects the common lead 2% at themake-before-break contact of this relay, for purposes as hereinafterwill he described.

lhe operation of relay causes also two circuits to be established, onefor relay 25 and another for relay and the stepping magnet 27. As relay25 is slow to operate, the circuit for relay 26 and operating magnet isthe one that operates first and may be traced as follows: battery,winding of mag net 27, armature and back contact thereof, to a commonpoint 28 and from battery through the winding of relay 26 to this common point 28, thence through middle right hand armature and frontcontact of relay 23, left hand armature and back contact of relay 25,the brush of switch 32, terminal 3%, outer right hand armature and frontcontact of relay 23 to ground. This causes the operation of relay 26which breaks the circuit for relay 25 and causes the stepping magnet 27to operate switch 1 and advance its brushes to connect with theterminals of the first trunk in a manner well known in the art.

If it is now assumed that the first trunk is idle, the circuit for relay26 and stepping magnet 27 will be broken at the terminal 3% andconsequently the stepping magnet will not advance the switch brushes anyfurther. The release of relay 26 in this case will close the originalcircuit for relay 25 which may be traced as follows: battery, winding ofrelay 25, armature and back contact of relay 26, innermake-before-breal: contact and right hand armature and front contact ofrelay 23, to ground, causing the relay to operate. The operation ofrelay now disconnects the brush of switch 2-32 from the circuit forrelay 26 and magnet 27 and connects it instead to the ground at theouter right hand armature and front contact of relay L3, thus making theterminal associated with this switch 32 and trunk No. 100 busy to otherswitches.

On the other hand, if it is asumed that trunk IN O/106 is busy whenbrush of the switch 32 connects with the corresponding terminal, it willbe seen that the ground from relay 23 of the corresponding associatedjacks will be connected to maintain relay 26 operated and cause thecontinued operation of magnet 27 to advance the brushes of the switch toa second trunk.

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The circuit inthis instance might-be traced as follows: from battery.through windings of magnet 27 and relay'26, through 'the'middle righthand armature and front contact of relay 23, left hand armature and backcontact of relay 25, brush of the switch 32, multiple lead 35 to thebrush ofthe switch corresponding to switch 32 of the switch throughwhich trunk No. has been engaged, and from there through the left handarmature and frontcontact of the relay cor responding to relay 25 to theouter right hand armature and front contact'of the re lay correspondingto relay 23, to ground. in this case therefore, the stepping magnet willhave taken two steps and connected the" jack 22 to the terminalsoftrunkNo. 101. It should benoted that relay 25 in operating also connects thetip and ring leads from jack 22 at its right hand armatures and frontcontacts to the brushes of switches 30 and 31 which now are connectedwith the terminals of the corresponding trunks such as 100 or 101.

The brushes of switch 33 are so shaped that they will bridge twoadjacent terminals. llhis is illustrated in Fig. 2 and is an importantpart of this invention as it will be seen that eventually when alltwenty trunks have been engaged by twenty jacks at various positionsincluding any combination of operators and switches as showndiagrammatically in Fig. 2, the brush of each engaged switch 33 willeach bridge two adjacent terminals and stand in such a position as tocompletely bridge all the terminals for all of the said twenty trunks,that is, one switch 33 will bridge terminals corresponding to trunks 100and 101, while the brush of another switch 33 will bridge terminalscorresponding to trunks 101 and 102, etc., so that the last trunkengaged will have the brush of the corresponding switch 33 bridgeterminals corresponding to trunks 118 and 119. As the correspondingterminals of all the switches 33 are multipled together and the terminal38 corresponding to trunk 119 is connected to ground as shown in thisFig. 2, a circuit will therefore be completed from this ground throughthe terminals of the twenty switches 33 and the multiple leads to acommon lead 36 which is connected through the winding of the commonrelay 50 to battery causing this relay to operate. Relay 50 in operatingremoves the ground through its armature and back contact and thusprevents not only any further conneo tions to be made through any of theunused jacks and the consequent operation of relay 23 but also connectsbattery to this common lead 24 so that battery potential will be appliedto all sleeves of the unused jacks, ex copt of course, the jacks of theswitches such as 100 and nineteen others that are used. That is, thejacks multipled from position to position'as, for example, thoseassociated with jack 22 will have a busy potential on' theirslieeves'from the battery of the cord circuit connected to jack '22. Itwill be seen that'in this manner'all the unused jacks will have a busypotential applied to their sleeves either from the armature of relay 5Oor'from the battery of the cordcircuits connected to the multiple jacksused.

If now one ofthe trunksbeconie idle by the IGlIlOVitlOftllG plug fromthe corre spondingjack, it will benoted that the bridge'con'ipletedthrough the brushes of the engaged switches 33 will be broken bythe'movement of the brush of the particular disengaged"switch 33 follows: acircuit will be completed torthe stepping-magnet 2'7 of thatswitclrthrou'gh the middle right hand armature and back' contact of thecor responding relay 23 tothe brush of the switch 33 of this tisengagedswitch to the ground in the bridge and thus advance the brushes of thisswitch one step and break the bridged connection. If the break in thebridged connection occurs at the nineteenth trunk, it is evident thatonly a single step will be taken by the magnet 27 but if the breakoccurs at some other trunk, the brushes of this particular switch willbe further advanced and intact returned to normal position as the groundfor trunk 20 will be supplied through this brush until its return tonormal position. If a switch not included in a closed chain circuitbecomes idle, then it remains where it is withoutmoving, but if thechain circuit is completed to it before it has again been taken for use,it will return to normal.

It is readily seen then that the busy test arrangement in accordancewith this invention may function with any straightforward trunkingarrangement in which. switches are employed regardless of the particular arrangement of the jacks in the various positions and boards aslong as the terminals of the switches 33 are multipled as indicated andthe brushes thereof are so constructed as to bridge adjacent terminals.

What is claimed is:

1. In a straightforward trunking system, a plurality of jack terminals,a corresponding number of automatic switches associated therewith, asmaller number of trunks available over said switches, a special bank ofterminals in each of said switches, with a terminal representing eachtrunk, said terminals being multipled from switch to switch and eachswitch being provided with a brush adapted to bridge two adjacentterminals, and a common busy testing means for establishing a busycondition at all jacks not used when all of said trunks have be comeengaged, said means being actuated when the terminals of the specialbanks oi the switches engaged form a complete bridge through all of theterminals representing said trunks.

2. In a straightforward trunking system, a plurality of jack terminals,automatic switches associated therewith, trunk lines accessible throughsaid switches, a common conductor, means forming part of each switch forcompleting a connection to ground for said common conductor when alltrunks are employed in connections, a relay associated with said commonconductor actuated when the ground is connected to said conductor, andmeans including a busy test conductor connected to a source of busypotential when said relay is operated to establish a busy condition atthe jack terminals not employed in the connections.

3. In a trunking system comprising a large number of jack terminals,corresponding switching means and a comparatively smaller number oftrunks accessible thereby, each of said switching means including aspecial switching bank having one terminal representing each trunk, saidterminals being multipled from one bank to another, a brush for each ofsaid banks arranged to bridge two adjacent terminals, a ground connectedat the last oi said special bank terminals at each of said banks, and abusy testing means actuated when all trunks are engaged and a completebridge is established at the switches used from a ground at one of thebanks through the bridged terminals of the banks of the switches used,for establishing a busy test condition at such jack terminals as are notused in the connections.

In witness whereof, I hereunto subscribe my name this 6th day ofFebruary A. D.,

LOUIS A. MORTIMER.

